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Interval Histograms and AHI
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SaviAtHome Offline

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Machine: PRS1 60
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Post: #1
Interval Histograms and AHI
Being familiar with statistics and new to CPAP, I have some questions about the interpretation and usefulness of AHI as an indicator. We are told that things are going well if we have an AHI of less than 5. Right now this doesn't like it is going to happen for me any time soon. An average AHI overnight of greater than 25 might seem bad enough, but what worries me more are apnea events lasting as long as 90 to 120 seconds and sometimes more! Suppose I can somehow manage to get my average AHI below 15, say, by having many good periods less than 5 but still end up with a significant number of events of much longer duration. I worry that the long duration apneas might be killing me (or permanently fogging my brain) just as fast as the high AHI.

One of the nice things about the SleepyHead software is that in addition to the graphs showing how AHI and other indicators change over time I can also see a complete list of all events with their durations. I was wondering if anyone has ever made use of this data to produce a histogram of the apea/hyponea events showing the event frequency relative to duration? People who know a thing or two about statistics would know that such "frequency distributions" are very important in many areas of science and engineering as a way of analyzing complex phenomena. Distributions with different shapes characterize quite different kinds of underlying processes and in this case perhaps different medical conditions.

Today I keyed the event data for 3 days into an OpenOffice spreadsheet and produced some histograms. I would like to share it with anyone who can do something similar so that we can compare them. Actually, I am also interested to find out if you think that this sort of graph might be a useful addition to the SleepyHead package. I know someone who could help with that.

Sleep well.
04-25-2013 07:20 PM
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buran Offline

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Machine: ResMed S9 Autoset
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Post: #2
RE: Interval Histograms and AHI
Yes, it is important and in fact it was implemented in MyEncore, a free addition to the old version of EncorePro. See multiple distributions here
lewiston.mit.edu/myencore/
You can download it, but it does not work with the current version of EncorePro.
So, to the best of my knowledge, no software currently exists that would do it out of the box.
But it is important. Apnea length can be 15sec or 1 min. AHI is the same in both cases, but health impact is different.
This is what I have now. AHI<5, but many apneas are around 30 sec, which leads to desaturations according to my oximetry data.
Adjusting my settings. Hope to fix it.
Anyway, you are right, it is important to look not only at AHI, but on the individual apnea length. Ideally to look at your flow rate waveform breath by breath.
(This post was last modified: 04-25-2013 11:45 PM by buran.)
04-25-2013 11:35 PM
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Sleepster Offline
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Machine: ResMed AirCurve10 VAuto
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Post: #3
RE: Interval Histograms and AHI
Welcome to the forum. MyEncore is an interesting package that seems to have escaped our notice around here. Surprising since it appears to have been around for about 10 years!

I see that it requires the EncorePro database, and you say the new EncorePro won't work. So what version of EncorePro will work? I have EncoreBasic and I'm guessing that won't do it, either.

Sleepster
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INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
04-26-2013 08:51 AM
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Sleepster Offline
Wiki Editor
Moderators

Posts: 4,993
Joined: Feb 2012

Machine: ResMed AirCurve10 VAuto
Mask Type: Full face mask
Mask Make & Model: F&P Simplus
Humidifier: HumidAir and SlimLine Hose
CPAP Pressure: MaxI 13.6 | MinE 5.2 | PS 4.4
CPAP Software: ResScan SleepyHead

Other Comments: Diagnosed Nov 2011. Conquered aerophagia.

Sex: Male
Location: Houston, Texas

Post: #4
RE: Interval Histograms and AHI
(04-25-2013 07:20 PM)SaviAtHome Wrote:  I was wondering if anyone has ever made use of this data to produce a histogram of the apea/hyponea events showing the event frequency relative to duration?

I can see how that would be a useful display of the data.

Unfortunately Mark Watkins (aka JediMark), the author of SleepyHead, seems to have slipped off the radar. It's open source so others can and have stepped in to make a patch to update it for the newer PRS1 machines.

If you have a friend who could pick it up and start working with it I know that there are people out there ready to donate.

Sleepster
Apnea Board Moderator
www.ApneaBoard.com


INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
04-26-2013 08:55 AM
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Shastzi Offline

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Post: #5
RE: Interval Histograms and AHI
I would suggest dumping the raw data into 'R', an open source statistical / graphing package.
There is a bit of a learning curve but hey, it's statistical software.

Smile

"With ordinary talent and extraordinary perseverance, all things are attainable." - Thomas Foxwell Buxton

Cool
04-26-2013 09:24 AM
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buran Offline

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Machine: ResMed S9 Autoset
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Mask Make & Model: Innomed hybrid
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Post: #6
RE: Interval Histograms and AHI
MyEncore was replaced with Encore Pro Analyzer,which is free and open source (MyEncore is not open source). I believe it is also outdated now, since the EncorePro database structure was changed. It all was discussed in details in another forum.
But I do not know anything specific, since I have ResMed, so it would not work for me anyway.
(This post was last modified: 04-26-2013 09:34 AM by buran.)
04-26-2013 09:33 AM
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